Physical and mechanical properties of pigeon pea, other grains and seeds are necessary for the design of equipment to handle, transport, process and store the crop. The physical properties of pigeon pea have been evaluated as a function of grain moisture content varying from 5% to 25% wet basis. In this seed moisture content range, the grain surface area, volume and sphericity decreased nonlinearly from 100.28 to 47.39 mm(2). 94 to 28 mm(3) and 0.91 to 0.82 respectively, while true density, bulk density and porosity increased nonlinearly front 0.75 to 1.22 g/mm(3), 0.70 to 0.87 g/mm(3) and 8% to 28% respectively. The 1000 seed mass, angle of repose and terminal velocity increased linearly from 96 to 140 g. 17degrees to 31degrees and 6.52 to 11.58 m/s respectively. The coefficient of static friction increased nonlinearly from 0.28 to 0.51 for plywood. 0.23 to 0.38 for galvanised steel and 0.18 to 0.31 for aluminium. (C) 2002 Elsevier Science Ltd. All rights reserved.